1. Field of the Invention
This invention relates to the use of elastic materials as a source of external power in orthotics and more particularly relates to the application of elastic forces in a knee extension assist device.
2. Description of the Prior Art
The current state-of-the-art in orthotics is limited almost exclusively to static control of the musculoskeletal system. As a consequence, freedom of useful motion, in terms of the immediacy of daily living, is constantly subjected to interference. However, removal of static protection often leads to an increase in deformities, followed by an inevitable decrease in daily activities.
In addition, elastic materials can store and deliver significant amounts of dependable energy. The ability to store energy is the most important characteristic of elastic materials for orthotic use. They can be made to produce a continuous force that can be employed in a manner that creates an orthotic system with dynamic forces. The fact that these dynamic forces can be varied in magnitude and made to serve a variety of purposes allows a versatility that far exceeds that of static orthotic systems.
The use of elastic materials as a source of external power can be useful in the development of a practical orthotic system of ambulation for paraplegics and other patients that would enable them to stand and walk with greater ease and confidence than present day static orthotic techniques allow.
The first step in developing a practical means of ambulation for a paraplegic is a system that will enable the patient to get to his feet in a quite conventional manner, starting with the knees flexed in a normal seated position.
Recent improvements in the design of dynamic orthotic systems have permitted the paraplegic patient to rise to a standing position. However, although up, the patient could not extend his knees fully so as to engage the knee locks of the bilateral knee-ankle-foot orthoses. Consequently, the knees buckled at each attempt to bear weight upon the legs. Therefore, further progress was not possible without a mechanism capable of automatically extending the knees and locking them in extension.
Attempts to extend the knee with elastic materials have been numerous with little or no success. The major problem has been that when enough force was applied to provide what could be considered functional extension when standing, the force inadvertently extended the knee when seated.
Accordingly, the primary object of this invention is to provide a practical dynamic orthotic system of ambulation for a paraplegic patient through the application of dynamic forces generated by elastic materials.
A related object is to provide an orthotic system employing dynamic forces to provide the patient with significant assistive force to aid in both rising from and descending to a sitting position.
Another objective is to provide a practical dynamic orthotic system for long-term protection of the musculoskeletal system from deformities without sacrificing the patient's freedom of mobility.
A still further object is to provide a knee extension assist device that may be employed by non-paraplegic patients such as polio victims or others lacking in the muscular structure to adequately extend the knee.